1. Field of the Invention
This invention relates to positively charged non-natural amino acids, methods of making them and their utilization in peptides.
2. Background
Synthetic studies have been directed toward understanding the influence that only some non-natural amino acids have on the structural and biological activity of peptides.
U.S. Pat. No. 3,178,472 to Hellerbach et al. discloses a method for the conversion of amino carboxylic acids to their N-monomethyl derivatives. Naturally occurring amino acids such as alanine, phenylalanine, serine, cysteine, cystine, tyrosine, tryptophan, histidine, methionine, valine, norvaline, leucine, isoleucine, arginine, ornithine, lysine, aspartic acid, glutaminic acid, threonine, α,γ-diaminobutyric acid and the like are suitable starting materials. When the starting material aminocarboxylic acid contains two amino groups such as lysine, ornithine or α,γ-diaminobutyric acid, then it is possible to generate a product in which one or both amino groups are methylated.
Moore et al. (Can. J. Biochem. 1978, 56, 315) discloses the effect of the basic amino acid side chain length and the penultimate residue on the hydrolysis of benzoyldipeptides by carboxylicpeptidase B1 (CPB). Non-natural amino acids including homolysine and homoarginine were incorporated into small peptide chains, and the kinetic parameters were determined for the CPB catalyzed hydrolysis of the peptide.
Lindeberg et al. (Int. J. Peptide Protein Res. 1977, 10, 240) discloses the synthesis of 1-deamino-4-L-valine-8-DL-homolysine-vasopressin and protected 1-deamino-4-L-valine-8-D-lysine-vassopressin in which with non-natural amino acids were incorporated. The addition of a methylene group to lysine and arginine to generate the non-natural amino acids homolysine and homoarginine, respectively. The study revealed that peptides with homolysine and homoarginine reduced the antidiuretic activity of the peptides.
Hilpert et al. (J. Med. Chem. 1994, 37, 3889) discloses screening of small basic molecules for binding in the recognition pocket of thrombin led to the discovery of the arginine mimetic (aminoiminomethyl)piperidine as a weak thrombin inhibitor. A number of derivatives of the arginine mimetic were prepared, and their ability to inhibit thrombin was assayed. The X-ray crystal structure analysis of thrombin as well as modeling studies of the arginine mimetic were conducted in order to rationalize the observed affinity between the unnatural amino acid and thrombin.
Nestor et al. (J. Med. Chem. 1988, 31, 65) discloses the synthesis of a new series of unnatural amino acids and their incorporation into antagonistic analogues of lutenizing hormone-releasing hormone (LH-RH). In particular, non-natural amino acids of arginine exhibited high acute potency and very prolonged duration of action. Biological and clinical pharmacology studies revealed that these LH-RH antagonists cause mast cell degranulation, and were removed from consideration as candidates for full commercial development.
There is a need in the art for non-natural amino acids and for peptides incorporating such acids to achieve superior effects, such as, for example, improved diagnostic or disease fighting activity. None of the above references discloses the non-natural amino acids of the present invention or the advantageous properties thereof. The present invention accordingly describes positively charged non-natural amino acids, methods of making them and their utilization in peptides.
Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.